FIG. 1 is a diagram schematically depicting the configuration of a communication system in which VoIP technology is introduced, i.e., a communication system in which voice data is transmitted using Internet protocols over a wireless access portion which corresponds to a link connecting between a mobile station and a base station. The communication system 1 includes mobile terminals UE1 to UE5, base stations BS1 and BS2, an access gateway ND (aGW) as an upper level node than the base stations BS1 and BS2, and a core network NT.
In the example depicted in FIG. 1, the base station BS1 covers an area A1, and is connected via logical channels to the mobile terminals UE1 to UE3 located within the area A1. On the other hand, the base station BS2 covers an area A2, and is connected via logical channels to the mobile terminals UE4 and UE5 located within the area A2.
Traditionally, priority control has been performed in the wireless access portion when allocating uplink bandwidth at the media access control (MAC) layer. In this priority control, time-sensitive data such as VoIP data is transmitted with relatively high priority, while less time-sensitive data such as email data is transmitted with relatively low priority.
For example, in the mobile terminal UE3 depicted in FIG. 1, when email data and VoIP data are input from an application layer 16 to a radio link control (RLC) layer 15 via application interfaces API#0 and API#1, respectively, the MAC layer 14 transmits the data to the base station BS1 by assigning higher priority to the VoIP data than the email data in accordance with the priority predetermined by the communication provider.
On the other hand, in the mobile terminal UE2, email data and Internet data are input from an application layer 13 to an RLC layer 12 via application interfaces API#0 and API#1, respectively. Since both the email data and the Internet data are low priority data, the MAC layer 11 of the mobile terminal UE2 requests uplink bandwidth with relatively low priority from the base station BS1. As a result, if the MAC layer 11 of the mobile terminal UE2 tries to transmit the email data preferentially, the bandwidth is preferentially allocated to the VoIP data of the other mobile terminal UE3 because the bandwidth allocation priority of the email data is lower than that of the VoIP data.
International Publication Pamphlet No. WO 2005/4076 discloses a configuration in which, in the event of a disaster, the bandwidth control apparatus preferentially assigns packet call bandwidth.
On the other hand, Japanese Laid-open Patent Publication No. 2006-229668 discloses a method that, in the event of a disaster, prompts users to use email when inquiring about the safety of their relatives.